Method of transmitting electric current from one body to another



United States Patent METHOD OF TRANSMITTING ELECTRIC CUR- RENT FROM ONE BODY T O ANOTHER Helge Oskar Kihlander and Carl Erik Foodge, Hallefors,

Sweden, assignors t Hellefors Bruks Aktieholag, Hallefors, Sweden, 21 company of Sweden N0 Drawing. Application October 8, 1953, Serial No. 385,029

Claims priority, application Sweden October 11, 1952 3 Claims. (Cl. 219154) connected directly to contact materials earlier known, for

example copper, can transmit the necessary current intensity. According to the present invention a conductive contact material is used, which is produced by pressing and/ or sintering iron powder or some other metal powder or by reduction of ore in the form of powder or pieces and which is easily mouldable by plastic deformation, the body with which good contact is to be obtained, being pressed into said contact material, so that the contact material is deformed through the contact pressure, whereby the contact surface is greatly increased in relation to the surface obtained when employing the method earlier known, and the contact surface can be completely utilized for the transmission of current. The current density is reduced and the material is uniformly heated. Also in the heating of other materials, for instance materials of unalloyed carbon steel the heat transmission is improved as is also the insensibility to difficulties caused by rough end surfaces.

The reason why it has proved impossible to heat materials of alloyed tool steel by means of resistance heating by employing methods already known, must be that point contact was obtained between the contact piece and the blank. The result was a punctal heating, and as steel is not sufliciently conductive to make away with the rapidly heated spot or spots, there will be a fusion, and the blank will be ruined.

A great number of experiments have proved that by using a suitable plastic, powder metallurgic contact material between the current conductors and the blank to be heated, for example iron or copper sponge, good cur- Patented Sept. 4:, 1515f;

rent-carrying contacts are obtained, whether the contact surface of the blank is rough or not. This is of particularly great importance when the transmission of current is intended for the heating of blanks to be rolled, when for natural reasons a rough end surface cannot be avoided. The contact material should be easily plastically deformable when the pressure is lower than 5 or 10 kgs./'mm. preferably lower than 2 kgs/mm In certain cases the pressure may be as low as 0.01 kg/mm or still lower, when loose powder is used. It is possible either to use fresh contact material for each heating operation or the contact material may be used for a number of operations. In the latter case contact material in the form of plates, for example of iron sponge, is preferred. Naturally the method according to the invention can be employed, not only when heating is concerned, but also for transmission of current for other purposes.

Having now described our invention, what we claim as new and desire to secure by Letters Patent is:

1. A method of transmitting electric current for the resistance heating of rolling or forging metal blanks comprising the steps of placing an electrically-conducting readily deformable sponge-metal contact material adjacent one of said blanks, pressing said blank into the spongy contact material so that said material is deformed to provide a large contact surface, and applying a resistance heating current to said blank through said spongy contact material.

2. A method of transmitting electric current for the resistance heating of rolling or forging steel blanks comprising the steps of placing an electrically-conducting readily deformable iron-sponge contact material adjacent one of said blanks, pressing said blank into the spongy contact material so that said material is deformed to provide a large contact surface, and applying a resist ance heating current to said blank through said spongy contact material.

3. A method of transmitting electric current as defined in claim 1 wherein said spongy metal contact is smeared or sprayed onto said metal blank.

References Cited in the file of this patent UNITED STATES PATENTS 1,665,367 Johnson et al. Apr. 10, 1928 2,013,585 Sciaky Sept. 3, 1935 2,248,280 Nobiron July 8, 1941 2,355,954 Cremer Aug. 15, 1944 2,425,052 Swinehart Aug. 5, 1947 2,467,636 Stoudt et al. Apr. 19, 1949 2,486,341 Stumbock Oct. 25, 1949 

